From a public health perspective, there is no more compelling crisis in the world today than the HIV epidemic in the developing world. This is a Phase III community-level randomized controlled study, in which 32 communities in Africa (Tanzania, Zimbabwe, and South Africa) and 14 communities in Thailand will be randomized to either a community-based HIV voluntary counseling and testing (CBVCT) intervention or clinic-based standard VCT (SVCT). The CBVCT intervention has three major strategies: (1) to make VCT more available in community settings; (2) to engage the community through outreach; and (3) to provide post-test support. These three strategies are designed to change community norms and reduce risk for HIV infection among all community members, irrespective of whether they participated directly in the intervention. Thus, a community-level sampling approach as opposed to a cohort design is used to evaluate outcomes. The primary aim (Aim 1) is to test the hypothesis that communities receiving 2-1/2 years of CBVCT, relative to communities receiving 2-1/2 years of SVCT, will have significantly lower prevalence of recent HIV infection. In addition, we propose the following secondary aim (Aim 2) to test the hypotheses that CBVCT communities, relative to SVCT communities, will at the end of the intervention period report significantly: a) less HIV risk behavior; b) higher rates of HIV testing; c) more favorable social norms regarding HIV testing; d) more frequent discussions about HIV; e) more frequent disclosure of HIV status; f) less HIV-related stigma; and g) less HIV-related social harm. Finally, because of the importance of cost-effectiveness data to host and donor countries, we propose to assess (Aim 3) the incremental cost-effectiveness of CBVCT compared to SVCT. A random sample of persons between the ages of 18 and 32 years of age from each community will be selected at baseline and post-intervention for measuring primary and secondary endpoints. Aim 1 will be evaluated by comparing the post-intervention prevalence of recent infection measured by the sensitive/less sensitive HIV assay on all positive HIV blood samples in the two arms of the study. Aim 2 will be evaluated by comparing a variety of behavioral measures at baseline and post-intervention. Aim 3 will be evaluated in terms of cost per HIV infection averted and disability-adjusted life years saved.